1. Field of the Invention
The invention relates to a thermostable edible composition having an ultra-low water activity. Specifically, the invention relates to a thermostable edible composition having an ultra-low water activity and containing an ultrahigh surface area particulate.
2. Description of the Related Art
The control of water activity in a food product can enable the food product to resist spoilage and maintain a fresh taste and mouth feel. The water activity of a food, or a food subsystem thereof, is a useful measurement of the degree of "freeness" of water contained in that food. Water activity is determined by the combined effect of the moisture content of the food as well as the nature of various components dissolved in an aqueous phase of the food.
The water activity (A.sub.w) of a food is defined as the partial vapor pressure of water in the food divided by the saturation vapor pressure of pure water at the temperature of the food. The water activity of a food can be measured by placing a sample of the food to be tested in a container. The container is then sealed and the relative humidity above the sample is determined after equilibrium is reached.
The relatively high water activities, that are associated with fillings and cremes made by standard formulations, permit microbial growth, moisture migration, and other problems to occur in a food product. Fillings and cremes with high water activities are, essentially, a medium for supporting microbial growth and, therefore, have limited shelf lives. Fillings and cremes with high water activities, generally, allow water to migrate into the surrounding foodstuff. When the surrounding foodstuff is a material of significantly lower water activity, such as a baked dough, the migration of moisture into the baked dough makes the baked dough "soggy." Low water activities are, usually, required in baked doughs in order to maintain a crisp and crunchy texture.
The incorporation of thermostable properties into fillings and other "food subsystems" often requires the use of stabilizers as flow control agents. Gums and other hydrocolloids are common stabilizers for aqueous food systems. Stabilizers provide flow control properties to aqueous food systems by altering the viscosity and texture of a food matrix. Stabilizers, such as gums or hydrocolloids, generally, must be "activated" in the water or moisture content of such food systems in order to be effective. Many gums, even when activated, do not provide suitable thermostability to an aqueous food system because the stabilization properties of the gum are affected and altered by temperature. Fillings, that are stabilized by gums, often flow at temperatures that are commonly used during food preparation such as baking.
Two types of gums or hydrocolloids are particularly effective in the preparation of thermostable fillings. A first group of gums form thermally irreversible gels. Thermally irreversible gels are useful in the preparation of "ovenable fillings" and are commonly prepared from high methoxy pectins. Thermally irreversible gels do not melt or flow unless they are exposed to temperatures that are significantly higher than the temperatures required for their original activation. A second group of gums alter the viscosity characteristics of an aqueous food system to render the aqueous food system essentially insensitive to temperature. An example of a viscosity altering gum is xanthan. Xanthan is a microbially-derived gum and provides viscosity properties to an aqueous food system. The viscosity properties are affected by stress or shear thinning rather than temperature. Viscosity altering gums provide an aqueous food system, such as fillings, that do not flow unless the temperature reaches the boiling point or the internal shear point of the aqueous food system.
Gums and other hydrocolloids, such as high methoxy pectin and xanthan, must remain activated within the water of an aqueous food system such as a filling. Typically, an aqueous food system must contain at least 20 percent moisture for these gums and hydrocolloids to remain activated. A gum or hydrocolloid is "activated" when it is in solution and functional. Therefore, gums and hydrocolloids are ineffectual as stabilizing agents in food systems that have moisture contents below about 15 percent.
U.S. Pat. No. 4,037,000 to Burge et al. discloses an icing mixture. The icing mixtures of Examples 3 and 4 of the patent are compositions containing glycerol and aqueous xanthan. These compositions include glucose syrup and can contain from 6.0 to 10.5 percent by weight of free water. This patent does not disclose a thermostable creme having an ultra-low water activity.
U.S. Pat. No. 4,670,272 to Chen et al. discloses a thermostable creme. The compositions of the creme of this patent can contain small concentrations of "polyols." The compositions of this patent contain high fructose corn syrup or standard corn syrup and can contain cellulose products. The water activity of the creme of this patent is "low" or has an A.sub.w value of 0.6 to 0.7. The compositions of this patent are aerated cremes wherein modified starch is activated by cooking and provides the stabilizing and texturizing properties to the food system. The creme of this patent does not have an ultra-low moisture content, ultra-low water activity, or shelf life of 9 to 12 months.
U.S. Pat. No. 4,752,494 to Tang et al. discloses a thermostable edible creme. The compositions of the creme of this patent can contain cellulose products, such as the Avicel.TM. product, and maltodextrin. The creme of this patent contains water from syrups or from water added to the creme. The added water can be in a concentration of up to 15 percent. Water must be present in a sufficient concentration to provide an "intermediate water activity base matrix" for calcium ions. The calcium ions and soluble caseinate of the creme of this patent stabilize and texturize the creme by forming a complexing gel between these two ingredients. The creme of this patent does not have an ultra-low moisture content, ultra-low water activity, or a shelf life of 9 to 12 months.
U.S. Pat. No. 4,774,095 to Kleinschmidt et al. discloses filling-containing, dough-based products. This patent discloses an aqueous-based composition, but the composition combines glycerin with cellulose products. The preparation of this patent obtains a thermostable filling which uses defibrillated cellulose as a thixotropic flow control agent to obtain a relatively low viscosity. High-methoxy pectin is further employed, as a gelling hydrocolloid, to reduce the "stringiness" that is caused by the defibrillated cellulose and to establish a thermally irreversible matrix to prevent "boil-out" in the oven. The continuous phase of this filling is an aqueous sugar solution. The sugar solution must be selected so as to avoid crystallization that can result in an undesirable texture and "mouth feel." The fillings of this patent have a water activity value below 0.5. The cellulose products, that are disclosed in this patent, are not "reactivated" in a non-aqueous polyol liquid in order to provide thermostability to the polyol liquid.
U.S. Pat. No. 4,861,604 to Tang et al. describes a sheetable thermostable filling composition. The composition for the sheetable filling is applied in a thin laminate form. The functionality of the disclosed composition is provided by gelatin, maltodextrin, and pregelled starch. An intermediate preparation is critical to obtaining a low moisture content and water activity in the final baked product. The filling of this patent does not provide a multi-purpose thermostable filling having ultra-low water activity.
The industry lacks a thermostable edible composition that has an ultra-low moisture content, an ultra-low water activity, and a shelf life of at least nine months. The industry further lacks a thermostable filling that has these properties and a total lipid content of 15 percent or less.